import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 7)
INF = float("INF")
MOD = 10 ** 9 + 7
MOD2 = 998244353
from heapq import heappop, heappush
import math
from collections import Counter, deque
from itertools import accumulate, combinations, combinations_with_replacement, permutations
from bisect import bisect_left, bisect_right
import decimal

n = int(input())
s = list(map(lambda x : 1 if x == "#" else 0, list(input().rstrip())))
ans = 0
ad = 0
dbl = False
for i in range(n)[::-1]:
    ans += 1
    if s[i]:
        if dbl:
            ad += 1
        else:
            dbl = True
    else:
        if dbl:
            dbl = False
        else:
            ad = max(0, ad - 1)
print(ans + ad)